Saw Blade

Saw blades for sawing of wood have traditionally been made with the flat side smoothly ground or coated with smooth rust-proofing lacquer, to reduce the friction between the saw blade and the sides of the kerf. It is also known to make the sides of the saw blade with sharp cutting or abrasive elements, to improve the smoothness of the cut surfaces by shaving or filing after the teeth have done their cutting, as described in the patents U.S. Pat. Nos. 4,102,231, DE 3 838 844 and SU 821136. Such saw blades create large friction and require large forces, and they have not been widely used.

According to the present invention a saw blade can be made with side surfaces, the structure of which assists in removing sawdust from the kerf without removing any substance from the cut surfaces. This lowers the friction considerably, and makes the saw blade less affected by lateral forces, thereby improving the smoothness and straightness of the cut.

A preferred embodiment of the present invention will be described with reference to the accompanying drawings, wherein like members bear like reference numerals, and wherein:

FIG. 1 is a cross-sectional view of a saw blade according to the present invention within a section of wood being cut; and

FIG. 2 is an enlarged cross-section of a portion of the saw blade substantially corresponding to the circle 2 in FIG. 1.

A section of a saw blade according to the invention is shown in the figure. The saw blade 10 may be part of a hand tool or of a power tool, such as a circular saw or a sabre saw. The saw blade is flat with side surfaces 12. Teeth 11 are provided along at least part of the periphery or edge, which teeth cut a kerf in the workpiece 17 with a width exceeding the thickness of the saw blade. The teeth 11 can be wider than the thickness of the saw blade or, as shown in the figure, set alternatingly to the left and right side of the length or circumference of the saw blade 10.

During sawing, sawdust 16 collects in the space 14 between the cut surfaces 13 of the wood 17 and the sides 12 of the saw blade, causing increased friction. If the sawdust is not equally distributed, it may force the saw blade 10 to one side causing a crooked or uneven cut.

During sawing with a saw blade of traditional type with smooth sides 12, each particle of sawdust 16 in the space 14 will be affected by a noticeable friction force from the cut surface 13 and by a very small force from the side 12 of the saw blade, with the result that the sawdust stays in the space 14. The saw dust 16 may gradually become compacted and adhere to the cut surface 13. The cutting force will increase until the saw blade 10 is lifted clear of the workpiece and the sawdust removed.

During sawing with a saw blade with abrasive or cutting elements on the sides, each particle of sawdust 16 will be affected by a noticeable friction force from the cut surface 13 and a very large force from the elements on the sides of the saw, with the result that the sawdust will slide and rub against the surface 13 but follow the motion of the saw blade with a strong tendency to adhere to the saw blade. The cutting forces increase when many particles adhere, and it may become necessary to lift the saw blade 10 clear of the workpiece to remove adhering particles manually.

A saw blade according to the present invention has side surfaces 12 with an organic coating surface structure which has a friction and graininess corresponding to the cut surfaces 13. Each particle or particles of sawdust 16 will be affected by equal friction forces from the cut surface 13 and from the sides 12 of the saw blade. This equal force provides the result that the sawdust particles keep rolling between the surfaces 12, 13 without adhering to either of them. The particles are finally transported out of the kerf with a velocity corresponding to one-half the velocity of the saw blade.

The surface structure according to the present invention is preferably achieved by dry powder lacquering to form a layer 15 on the side surfaces 12 of the saw blade. The grain size and firing temperature of the lacquer is chosen to give a grainy surface with a grain size about 0.3 to 0.6 mm and a profile depth about 0.15 to 0.05 mm peak to peak. Suitable types of lacquer are epoxy, polyester or mixtures of these. This surface layer 15 feels clearly uneven to the touch. The convex grain surface peaks 18 should be more rounded than the concave grain surface troughs or valleys 19 to minimize abrasion. The thickness of the layer 15 should be less than the amount of set of the saw teeth 11 to ensure sufficient space 14 between the cut surface 13 and the lacquer layer 15.

Tests with a saw blade with grain size 0.5 mm and profile depth about 0.07 to 0.10 mm in resinous wood show that the cutting force is lowered by 20% and that no sawdust adheres to either the cut surfaces 13 of the wood 17 or the sides 12 of the saw blade 10.

The invention can be applied to any kind of saw blade which is not appreciably deformed during sawing, such as handsaws, sabre saws and circular saws, but not to bandsaws which for their proper guidance depend on sliding contact with metallic guide devices.

The principles, preferred embodiment and mode of operation of the present invention have been described in the foregoing specification. However, variations and changes may be made by others without departing from the spirit of the present invention. Therefore, all such variations and changes that fall within the scope of the claims appended hereto are intended to be embraced thereby.